Brother and Sister
by Hobbitgirl23
Summary: What if Marty McFly had a younger sister that he took with him on his adventures?**CURRENTLY ON HIATUS**
1. Chapter 1

**DISCLAIMER: I DON'T OWN ANYTHING BACK TO THE FUTURE**

Katelyn is Marty Mcfly's 14 year old younger sister. They are very close and do pretty much everything together. Earlier today they received a call from Doc telling them to meet him in the parking lot of Twin Pines Mall at 1:15.

"Wh...wha?" she said blearily. "Come on Katelyn, it's almost 1:15" Marty shook her arm again. She looked up at him, half asleep. "5 more minutes mommy" she said and buried her head into her pillow. Marty rolled his eyes, smirked, and pulled the covers off of her. Katelyn sat straight up, "hey!" she yelled. "Come on we're going to be late", he said pulling her out of the bed.

They skateboarded into the Parking lot at 1:17. Doc's big white van was there but there was no sign of him, just Einstein sitting outside. "Hey boy where's Doc?" Marty asked petting him. All of a sudden, the back door of the truck lowered down and out came Doc driving a... DeLorean? "Marty! Katelyn! You made it!" Doc said climbing out of the car. "Welcome to my latest experiment this is the big one, the one I've been waiting for all my life. Alright roll tape!" Marty pulled out the video camera and started recording. "Good evening I'm Doctor Emmet Brown. I'm standing in the parking lot of Twin Pines Mall. It's Saturday morning October 26, 1985, 1:18 am. This is temporal experiment number one.

Katelyn watched as Doc led Einstein to the car and buckled his seat belt. He closed the door and then took out a remote. "You've got that thing hooked up to the car?" Marty asked. Doc ignored him and drove the car down the parking lot and turned it around facing them. Doc smirked," If my calculations are correct, when this thing hits 88 miles per hour you're going to see some serious s**t" Katelyn smiled and stood next to Marty gripping his arm nervously. You never could tell when one of Doc's experiments would go haywire. Doc revved up the car and started driving it straight towards them. Marty tried to walk out of the way, pulling Katelyn with him, but Doc pulled him back. "Watch this", he said. The car got closer and closer and when it was only a couple of feet from them, it disappeared, leaving a trail of fiery tire tracks behind. The license plate from the DeLorean had fallen off, the only thing left of the car.

Katelyn gawked at the sight and Marty stood looking in disbelief at the license plate. Doc was busy excitedly babbling in the background. "Jesus Christ Doc! You disintegrated Einstein!" Marty shouted. "Calm down Marty I didn't disintegrate anything" Doc said," the molecular structure of Einstein and the car are completely intact!" "Then where the hell are they?" Katelyn shouted. Doc looked back at her, "The appropriate question is when the hell are they! You see Einstein has just become the world's first time traveler. I sent him one minute into the future to be exact. And at precisely 1:21 and zero seconds we will catch up with Einstein and the time machine!" Marty and Katelyn looked at Doc in disbelief. "So your telling me you built a TIME MACHINE... out of a DeLorean?" Marty said out of breath.

"Watch out", Doc yelled and pushed Katelyn and Marty out of the way. The DeLorean appeared in the exact spot they were standing before. Doc opened the door and out jumped Einstein. "Well guys here I go to the future!" Doc said throwing his suitcase into the car. "Hey Doc", Marty said, "Look us up when you get there." Doc smiled, "I will….Oh I almost forgot the extra plutonium to power the car!" he said getting out of the car. "Hey by the way Doc where did you get that stuff?" Marty asked. "A bunch of Libyans asked me to make bombs for them. I stole the plutonium and gave them bombs made out of cheap pinball parts", Doc laughed.

Suddenly, Einstein started barking. "What is it boy?" Doc asked, following the direction Einstein was looking. "Oh my God they found me I don't know how they did but they found me! Run for it kids!" "Who?" Katelyn and Marty said simultaneously. "Who do you think? The Libyans!" Doc said getting out a gun. The Libyans were driving quickly while shooting at Doc. "Holy s**t! " Marty yelled pulling Katelyn down against the DeLorean. Doc ran to the back of his truck. "Doc wait!" Marty yelled but it was too late the Libyans had him cornered. Doc threw up his gun in defeat but they Libyans shot him anyway. Marty stood up "no! You idiots!" The Libyan turned to Marty. Katelyn stood up, grabbed Marty, and pulled him in front of Doc's truck.

"We have to get out of here!" Katelyn whispered. "Yeah I know!" Marty said pulling her to the other side of Docs van. The Libyans pulled in front of them and Marty stepped in front of Katelyn, eyes closed preparing to be shot. He was a little confused when nothing happened.

Katelyn peered over his shoulder and saw that the gun wasn't working. She quickly took Marty by the hand, and ran with him to the DeLorean before the gun started working again.

They both got inside and Marty started driving with the Libyans behind them in hot pursuit. "Alright let's see if these morons can reach 90" Marty said. Katelyn held tightly to her seat and looked at the side mirror. "MARTY!" she yelled. Marty looked out the window "crap!" The Libyan shooter had taken out a missile and was aiming it at the car but he never got to shoot.

The speedometer of the DeLorean read 88 mph and suddenly Marty was struggling to gain control of the car in a field. He ran into a scarecrow which landed on the windshield. Marty and Katelyn both screamed. The scarecrow flew off and they saw that they were headed straight for a barn. They screamed again before they crashed into it and silenced on impact. Marty groaned, "Are you okay Katelyn?" Katelyn coughed,"Yeah I think so" They both climbed out of the car. The barn door was open and there was a man with a gun standing there with children hiding behind him.

"Pa what are they?" a girl asked. "They're aliens!" the boy shouted, "and they've already mutated into human form! Shoot them!" The man started shooting at them.

Marty dove back inside the car while Katelyn jumped behind a hay bale to dodge a bullet that just whizzed past her ear. Marty opened the passenger door. "Get in!" he shouted. Katelyn peered out from her hiding spot, ran into the DeLorean and closed the door.

Marty stepped on the gas and burst through the wall of the barn he kept driving until the car died in front of a sign that read Lyon Estates. "Where's our house?" Katelyn asked. "It hasn't been built yet", he replied, sighing. "We don't want anyone to see this", he said getting out to push the car behind the sign. "We need to find 1955 Doc so he can help us find a way to get back home. And we have to make it to Hill Valley, so we better start walking."


	2. Chapter 2

**DISCLAIMER: I DON'T KNOW ANYTHING BACK TO THE FUTURE**

"That would have been much faster if we'd had our skateboards", Katelyn said huffing. "Tell me about it", Marty wiped the sweat from his forehead. "I guess we'd better find Docs number somewhere.

It was crazy how different the town looked. There was a nice grassy spot where the big parking lot was in 1985. The cars were older and the clock tower was actually working.

Marty saw a café across the street. "There's got to be a phone book in there", he pointed.

When they walked in the place, they didn't see any customers but a lone person at the bar. "You jump ship kid?" the bartender asked, looking at Marty's vest. "Excuse me?" "What's with the life preserver?" he nodded towards Marty. "Look we just need to use the phone", Marty said.

"Ah ha, here he is", Marty started to dial the number into the phone. "Come on Doc answer!" Marty slammed the phone down. "He's not there"

Katelyn turned around,"Hey do you know where 1640 Riverside..."

"You kids gonna order something or what?"

"Yeah give me a Pepsi free", Marty said walking over to the bar.

"If you want a Pepsi your gonna pay for it", the bartender said defensively. "Look just give me something with no sugar ok?" Marty retorted. "And what do you want?" he asked Katelyn. "I'll just have a water", she said. The bartender gave her the water and gave Marty some coffee.

"Hey Mcfly!" someone said coming in the door. Katelyn, Marty, and the person next to them all turned around. "What do you think you're doing?" he said strolling in. Marty looked at Katelyn wide-eyed, "Biff", he said

"Hey I'm talking to you McFly, you Irish Bug", Biff said walking over to the person next to Marty who stood up. "Oh hey Biff, hey guys how are you doing?"

"You got my homework finished McFly?"

"Uhh actually I figured since it wasn't due until Monday...", but he didn't get to finish because Biff grabbed his head and started knocking on it."Hello! Think Mcfly, think." he said releasing him.

The teen laughed but it was a fake one. "I gotta have enough time to recopy. Do you realize what would happen if

I turned in my homework in your handwriting? I'll get kicked out of school. You wouldn't want that to happen. Would ya?" Biff said angrily. The teen hesitated and Biff grabbed him by the shirt, "Would Ya!?" "No I wouldn't want that to happen", the teen said. Biff turned and looked at Katelyn and Marty who were now staring at the teenager next to them, who they now realized was their dad, "What are you looking at buttheads?" One of Biff's goons pulled at Marty's vest. "Hey Biff get a load of this guy's life preserver. Dork thinks he's gonna drown." Biff and his gang laughed. Katelyn normally would have defended Marty, but she was too busy staring in awe at a younger version of her dad.

Biff turned back to George. "So what about my homework McFly?" "Ok Biff, well I'll finish that up tonight and I'll bring it over first thing tomorrow morning", George said, eating a spoonful of cereal. "Yeah not too early, I sleep in on Sundays... Hey McFly your shoe's untied" George looked down and Biff slapped him in the face. His gang laughed. "Don't be so gullible McFly. I don't want to see you in here again." Then Biff and his gang left.

Marty and Katelyn kept staring at George as he ate until he put his spoon down and looked at them annoyed. "What?"

"You're George McFly!"

"Yeah and who are you?"

Before Marty could say anything, a worker came up to George.

"Why do you let those boys push you around?"

"Well they're bigger than me."

"Stand tall boy, have some respect for yourself. Don't you know that if you let people push you around, they'll push you around their whole life! Look at me, do you think I'm gonna spend the rest of my life in this slop hole?"

"Watch it Goldie", the bartender said.

"No sir, I'm going to night school, and make myself something. "That's right he's going to be mayor!" Marty blurted out."Yeah I'm gonna be...mayor! Now that's a good idea, I could run for mayor!" "A colored mayor, that'll be the day." the bartender laughed.

"Just you wait Mr. Caruthers, I will be mayor and I'll be the

most powerful mayor in the History of Hill Valley. I'm going to clean up this town. "Good, you can start by sweeping the floor." the bartender said, handing him a broom.

Marty and Katelyn heard a bicycle bell outside and looked out the window. George got on his bike and drove off. Marty immediately got up and ran after him. "Da... George... Hey you on the bike!" Katelyn ran out after him. "Hold up Marty!"

They ran for quite some time before Marty stopped and looked up. George McFly was sitting in a tree with binoculars watching a girl get undressed. "He's a peeping Tom!" Marty said in disbelief. Katelyn gasped as George slipped and fell onto the road as a car was coming by. "Dad!" Marty yelled and pushed him out of the way. "Marty!" Katelyn screamed as he was knocked over by the car and passed out. She ran over to Marty as the man, her grandpa, got out of the car. "Do you know him?" the man asked her. "Yeah he's my brother", Katelyn said as she saw her dad run off. "Stella! Another one of these crazy kids jumped in front of my car! Come on out here and help me take him in the house!" her grandpa yelled.

Katelyn wouldn't leave Marty's side no matter what and so when Lorraine insisted on Marty being put in her room, Katelyn followed. She tried to stay awake sitting on a chair next to the bed Marty was in, but she was tired and Marty wasn't waking up anytime soon, so she eventually fell asleep.

Katelyn woke up when she heard a loud bang. She bolted upright in her chair and saw that it was Marty... Putting his pants on? "Why where your pants not on?" she asked groggily. "Mom took them off of me while I was sleeping", Marty said.

"Ew gross"

"Yeah think how I feel"

They came down to the dining room with Lorraine and her mom, their grandma. "Sam, here's the young man you hit with your car out there." Stella said. "Why were you in the middle of the street?" he asked Marty grumpily. "Don't listen to him, he's in one of his moods." she told Marty, offering them each a seat at the table. "You can sit next to me", Lorraine said, pushing Marty into the seat next to her

Sam was fiddling with the TV set until he got a clear picture and rolled it into the dining room. "Our first television set, dad just picked it up today. Do you have a TV?" Lorraine asked Marty who was sitting next to her.

"Well yeah you know we have two of them."

"Two? You must be rich!" one of Lorraine's brothers exclaimed.

"Oh honey, he's just pulling your leg. Nobody has two televisions." Stella said, thinking Marty was joking. "Hey I've seen this! This is when Ralph dresses up as the man from space. This is a classic." Marty said watching the tv.

"What do you mean you've seen it? It's a new episode." one of the kids said.

Marty quickly realized his error," I saw it on a rerun"

"What's a rerun?"

"You'll find out", Marty muttered.

"Katelyn, I feel like I've seen you before", Stella said. "Do I know your mother?"

Katelyn looked at Marty,"umm... I think you might." "Oh I better give her a call then. I don't want her worrying about you two. "You can't! ... Um nobody's home that is.", she quickly recovered.

"Hey do you know where Riverside Drive is?" Marty asked, eager to change the subject.

"That's at the other side of town; a block past Maple." Sam said with food in his mouth.

"Block past Maple. Isn't that John F Kennedy Drive?" Marty asked.

"Who the hell is John F Kennedy?" Sam asked.

Lorraine broke the silence, "Mother, with Marty's parents out of town, don't you think he should spend the night? After all dad did hit him with the car." Katelyn cringed at the sight of her mom gawking over Marty.

"That's true, I think they should stay over." Stella said, turning to Marty and Katelyn. "I feel like you're our responsibility."

"Ahh gee I don't know..." Marty said fidgeting.

"Marty can sleep in my room!" Lorraine said excitedly, squeezing Marty's knee. Marty shot up out of his chair

"Ah...I have to... We have to go!" he stammered. "Come on Katelyn. Thanks for everything. I hope we'll see you later."

Marty and Katelyn bolted out the door. "Much later", Marty muttered as he closed the door.


	3. Chapter 3

**DISCLAIMER: I DON'T OWN ANYTHING FROM BACK TO THE FUTURE**

Marty and Katelyn ran up to 1640 Riverside Drive and knocked on the door. Doc opened it slightly, peered out, and then closed it again.

"Doc?" Marty said as Doc opened the door again.

Doc was wearing a weird contraption on his head. "Don't say a word", he said, pulling Katelyn and Marty inside.

"Doc!"

"I don't want to know your names, I don't want to know anything about you!" Doc scrambled about.

"Listen Doc..." Marty started.

"Quiet!" Doc yelled as he stuck a suction cup thing on both Marty's and Katelyn's heads.

"I'm going to try to read your thoughts." Doc said confidently "Let's see... Now you've come here from a great distance."

"Yeah! Yeah!" Katelyn said excitedly.

"Shhh don't tell me! You want me to buy a subscription to the Saturday Evening Post?"

Marty's face fell, "No, no"

"Not a word not a word not a word Quiet", Doc said trying to concentrate. "You want me to make a donation to the Coast Guard Youth Auxiliary."

"Doc", Marty said, ripping the suction cup off, "We're from the future. We came here in a time machine that you invented, and we need help to get back to the year 1985."

Doc turned to Katelyn, pulled the suction cup off of her, and put his hands on her shoulders. "Do you know what this means?" he asked. "It means that this damn thing doesn't work at all!" he yelled taking his weird helmet off.

"Doc you gotta help us! You're the only one who knows how your time machine works!" Katelyn said, following him.

"Time machine? I haven't invented any time machine." Doc whispered.

"I'll prove it to you." Marty said, taking out his wallet. "Look at my driver's license. Expires 1987. Look at my birthday for crying out loud! I haven't even been born yet! And look at this picture. My brother, my sister, Katelyn, and me. Look at my sister's sweatshirt Doc. Class of 1984."

Doc looked at the picture. "Pretty mediocre photographic fakery. You cut off your brother's hair." he said throwing the picture aside.

"I'm telling the truth Doc, you gotta believe me!"

Doc stood up, "Then tell me future children, who's president of the United States in 1985?"

"Ronald Reagan", Katelyn answered

Doc looked at her, "RONALD REAGAN! THE ACTOR? Ha! Who's vice president? Jerry Lewis?" Doc started outside with Marty and Katelyn behind him.

"I suppose Jane Arvin is the first lady!"

"Whoa wait Doc!"

"And Jack Benny is secretary of the treasury!" Doc opened the door to his garage.

"Wait Doc! You've gotta listen to us!" Marty said catching up

"I've had enough for one evening!" Doc started closing the door," Goodnight Future Children!"

Marty went up to the closed door, "Doc, the bruise, the bruise on your head! We know how that happened you told us the whole story! You were standing on your toilet and you were hanging a clock and you fell, and you hit your head on the sink, and that's when you came up with the idea for the flux capacitor. Which is what makes time travel possible." Marty banged on the door in defeat.

Doc opened the door, eyes wide staring at the two kids. "Come in quickly!"

They pulled up to the Lyon Estates sign. "There's something wrong with the starter so I hid it here." Marty said, walking behind the sign. He started taking the branches off the car that he used for camouflage.

"After I fell off my toilet, I drew this." Doc showed his drawing of the flux capacitor to Katelyn and Marty.

"The flux capacitor", Katelyn said, opening the door and flipping a switch.

Doc gasped when he saw it. "It works! Haha! I finally invent something that works!"

"So how are we gonna get this thing back anyway?" Katelyn asked. Just then, Doc got in the DeLorean, turned the keys, and the engine started. "Of course it decides to work now." Marty rolled his eyes.

Marty finally got the video camera hooked up to the TV. "Hey Doc this is it"

Doc came over, "Why that's me! Look at me I'm an old man! Thank God I've still got my hair. What on earths that thing I'm wearing?"

"That's a radiation suit." Marty answered.

"Radiation suit? Of course! From the fallout of the atomic wars!" Doc said excitedly.

"Yeah sure", Katelyn said.

"This is truly amazing!" Doc examined the camera. "A portable television studio. No wonder your presidents an actor he has to look good on television."

"Woah this is it this is the part coming up Doc", Marty stopped the tape as Doc was explaining how the car worked.

"What did I just say?" Doc said, making Marty rewind the tape.

"1.21 gigawatts!?" Doc stood up. "1.21 gigawatts!" he started for the door. "Great Scott!" he said, and made for the house.

Marty and Katelyn ran after him. "Wait a minute Doc!" Katelyn yelled.

"What the hell is a gigawatt?" Marty called after him.

"How could I have been so careless? 1.21 gigawatts." Doc picked up a picture of Thomas Edison. "Tom, how am I going to generate that kind of power? It can't be done it can't!"

Marty and Katelyn ran in. "Doc! Look, all we need is a little plutonium." Marty said.

"Oh! I'm sure that in 1985 plutonium is available in every corner drugstore, but in 1955, it's a little hard to come by!" Doc put his arms on Katelyn and Marty's shoulder. "Marty, Katelyn, I'm sorry, I'm afraid you're stuck here." he plopped down in his chair.

"Woah whoa stuck here? We can't be stuck here! We've got lives in 1985!" Marty sat down across from Doc.

"Yeah I've got my friends!" Katelyn said.

"And I've got a girl!"

Doc looked up. "Is she pretty?"

"Ah she's beautiful." Marty took out the clock tower flyer he had gotten back in 1985. Jennifer had written her number on it for him. "She's crazy about me! Look at this look what she wrote here Doc, I mean, that says it all." Marty showed Doc the paper. It said "love you" under Jennifer's number.

"Doc, you're our only hope." Katelyn looked at him desperately.

"I'm sorry kids, but the only thing powerful enough to generate that energy is a bolt of lightning."

Marty looked at Doc. "What'd you say?"

"A bolt of lightning. Unfortunately, you never know when or where it's going to strike!"

Marty looked at the flyer and handed it to Doc again. "We do now."

Doc read it. "This is it!" Doc got up. "This is the answer. It says here that a bolt of lightning is going to strike the clock tower at exactly 10:04 PM next Saturday night!"

"If we could somehow harness this lighting. Channel it into the flux capacitor... It just might work. Next Saturday night we're sending you back to the future!"


End file.
